Effects of Electron Donor Additives to Sewage Sludge on Biomethanation of Gaseous Carbon Dioxide

Abstract

This study investigated the effect of concentration on biomethanation in electron donor additives (zero valent iron (ZVI) 10-40 g/L, activated carbon (AC) 1.0- 4.0 g/L and Fe₃O₄ 0.25-1.0 g/L) when carbon dioxide (CO₂) is the only carbon source in anaerobic digestion., and the researchers estimated the pathway of CO₂. ZVI had 43-49 % biomethanation of injected CO₂ but was not observed in AC and Fe₃O₄. It has been confirmed that the rate of hydrogen (H₂) production from ZVI depending on its size. Furthermore, when there is a shortage of CO₂, inhibition occurs due to the hydrogen generated from ZVI. The reason for the inhibition of methane (CH₄) production in AC and Fe₃O₄ was found to be due to volatile fatty acids (VFAs) accumulation. The use of additives induces the conversion of CO₂ to VFAs and inorganic carbon, which are necessary for biomethanation. The addition of ZVI increased the growth of hydrogenotrophic methanogens, thereby enabling CH₄ production without VFAs accumulation.